Reservoirs of dense atomic gas (primarily hydrogen), contain approximately 90 percent of the neutral gas at a redshift of 3, and contribute to 2-3 percent of the total baryons in the Universe. These damped Lyman-${ \alpha}$ systems (so called because they absorb Lyman-${ \alpha}$ photons from within and from background sources) have been studied for decades, but only through absorption lines present in the spectra of background quasars and gamma-ray bursts. Such pencil beams do not constrain the physical extent of the systems. Here, we report integral-field spectroscopy of a bright, gravitationally lensed galaxy at a redshift of 2.7 with two foreground damped Lyman-${ \alpha}$ systems. These systems are $>$ 238 $kpc^2$ in extent, with column densities of neutral hydrogen varying by more than an order of magnitude on $<$ 3 kpc-scales. The mean column densities are $10^{ 20.46}$ - $10^{ 20.84} cm^{ -2}$ and the total masses are $> 5.5 \times 10^{ 8}$ - $1.4 \times 10^{ 9} M_{ \odot}$, showing that they contain the necessary fuel for the next generation of star formation, consistent with relatively massive, low-luminosity primeval galaxies at redshifts $>$ 2.
Categories: astro-ph.GA